1. Field of the Invention
This invention relates to gas turbine engines for aircraft and more particularly to such engines which include a bypass duct between an outer wall or nacelle and the center body of the core engine and which include blocker doors for diverting air from the bypass duct for thrust reversal.
2. Description of the Prior Art
A conventional thrust reverser for high bypass turbofan engines employs a cascade configuration covered by blocker doors when the thrust reverser is not in use, that is, during normal operation of the engine. These conventional thrust reversers have a disadvantage in terms of excess weight. The art has sought to overcome this deficiency by providing lighter weight blocker doors for thrust reversal in order to improve efficiency and to facilitate movement of the doors between normal and thrust reversal position. Unfortunately the development of such doors, while accomplishing the initial objectives just discussed, has introduced other disadvantages, particularly that the lighter weight door approach has resulted in pits on the inner surface which cause pressure drops in the exhaust flowpath during normal operation and result in a specific fuel consumption loss. Further the turbulence developed in this pit area has provided a potential noise source and this runs contra to one of the desired objectives of modern aircraft engines, namely, the reduction in noise of such engines.
The present invention retains the benefits of such lighter weight doors but eliminates the disadvantages of the aforementioned pits by providing arrangements for automatically covering the pits when the blocker doors are in the position they occupy during normal operation of the engine, that is, when forward thrust is desired. Further, this benefit is achieved without sacrificing the desired light weight construction of the blocker doors or interfering with the efficient movement of the doors between the normal and thrust reversal positions or significantly reducing flow of air along the blocker doors during thrust reversal operation.
Accordingly, it is an object of this invention to provide a thrust reverser for a gas turbine engine which employs light weight blocker doors for thrust reversal and which provides arrangements for covering the pits present in such light weight doors when the doors are in the position for normal operation of the engine, thereby minimizing pressure drop in the bypass duct during such normal operation and improving specific fuel consumption.